Conventionally, a tandem-type image forming apparatus, which is structured so as to array a plurality of image forming units that form an image with individually different colors (for example, yellow, magenta, cyan, and black) in series along a conveying path of a recoding medium, is known.
Further, in the above-described tandem-type image forming apparatus, a structure has been also proposed, which is an upper frame (an image forming housing) incorporated these image forming units and make higher in rigidity than a lower frame (a sheet feeding housing) which loads the upper frame.
If the above-described frame structure is adopted, for example, a recessed part and a projection part on an installation site can be absorbed by distortion of the lower frame which is lower in rigidity. Therefore, the upper frame can be prevented from being twisted or distorted without increasing the rigidity of the frame as a whole. Then, the positioning accuracy can be kept high between the image forming units.
Moreover, in this type of image forming apparatus, upon installation of a sheet feeding mechanism equipped with movable components such as registration rollers. There is a case where the movable components and others are installed in advance on a resin-made frame (hereinafter, also referred to as a sheet feeding frame) and this sheet feeding frame is mounted on the upper or lower frame.
In the above-structured image forming apparatus, after the registration rollers are used to position the leading end of a recording medium, the recording medium is sent to the downstream side of a conveying path extending in a front-rear direction, and thereby fed to image forming unit may be adopted. In this instance, in order to form an image at an appropriate position on the recording medium, it is important to accurately position a relative position between “the sheet feeding frame into which the registration rollers are incorporated” and “the upper frame that support the image forming unit” in the front-rear direction (in other words, a direction in which the recording medium is sent).
However, there is a case where the upper frame is structured to have a pair of sheet-metal components that the pair of sheet-metal components is punched out respectively toward a right-left direction and installed upright spaced in the right-left direction and the sheet feeding frame is arranged between the pair of sheet-metal components. In this case, it is not necessarily easy to accurately position the sheet feeding frame relatively with respect to the upper frame in the front-rear direction.
For example, there is a case where the sheet feeding frame is positioned in the front-rear direction by contacting the sheet feeding frame to come into contact directly with a pair of the sheet-metal components arranged in parallel on both sides of the sheet feeding frame. In this case, it is necessary to form projections that is projecting from the sheet-metal component to the sheet feeding frame, or projecting from the sheet feeding frame to the sheet-metal component, such that the pair of the sheet-metal component and the sheet feeding frame come into contact therewith.